“GIS data is categorised as vector and raster data. GIS is heavily reliant on quality data to produce meaningful maps and analysis.”
In this module, we look at the various sources of GIS data that can be used in any GIS software.
The list below shows open source data source available in South Africa.
1. NGI - Custodian of 1:50 K,1:250 K vector and raster data sources. NGI also provides raster data sources namely DEM of various resolution.
2. Surveyor General - provides a map of all land parcels and administrative boundaries in South Africa. It shows the relationship of every piece of land to those adjoining it. In addition, other surveyed real rights such as servitudes and leases are also included in this map.
3. Demarcation Board - provides all administrative data for South Africa.
4. Government Departments - Most government departments have websites that provide access to data in the specific domains they specialise in e.g. Water Affairs.
5. Municipalities - Various municipalities in South Africa provides online portals where users can download data. Example, Cape Town.
Global Data sources
1) Natural earth - is a public domain map dataset available at 1:10m, 1:50m, and 1:110 million scales. Featuring tightly integrated vector and raster data.
2) OSM - Open Street Map is a collaborative project where users capture data and upload it online. This data can be downloaded directly in QGIS using plugins ie Quick OSM.
3) Landsat - provides remote sensing data.
4) Open Topography - provides a portal to high spatial resolution topographic data and tools.
5) Esri Open Data
6) USGS Earth Explorer - provides remote sensing data.
7) NASA's Socioeconomic Data and Applications Center (SEDAC) - provides data that deals with human interactions with the environment.
Goal: To explore OSM data and add various map backgrounds
NB You need to be connected the internet in order to download plugins and fetch base maps from the provided URL.
To Do: Play around with the Quick OSM plugin and add various query combinations so that you can understand more about OSM data.
Spatial data can either be vector or raster. Each type of spatial data can further be differentiated by the format in which the data it provides. Each GIS software has the ability to read and write different data source type. At the heart of any GIS analysis is spatial data. In the open source world, the emphasis is on empowering users with the tools(QGIS) and data to do analysis and create maps. Whilst data is freely available care should also be taken in identifying data that is clean and useable within any analysis. Users should also read the metadata that describes the characteristics of the data and the licence agreement that comes with the data.
The data sources provided above are not exhaustive and users should try to search the web for other additional data sources but this provides a starting point when looking for open source data.